EP greases are formulated to lubricate under highly loaded conditions and require highly effective EP additives to prevent scoring and welding. Antimony diamyldithiocarbamate and thiadiazole/poly(ether)glycol complexes are compounds that have been found to be effective EP grease additives. Representative patents disclosing the use of antimony diamyldithiocarbamate in grease are U.S. Pat. No. 3,139,405 and U.S. Pat. No. 5,246,604, which are incorporated herein by reference. U.S. Pat. No. 6,365,557 discloses thiadiazole/poly(ether)glycol complexes that are produced by heating 2,5-dimercapto-1,3,4-thiadiazole (DMTD) directly in poly(ether)glycol diluents. Although antimony diamyldithiocarbamate and thiadiazole/poly(ether)glycol complexes are excellent extreme pressure additives, these compounds will corrode and/or tarnish copper.
United States Patent Application 20060183648 discloses the use of 1 to 1 (mass to mass) antimony and zinc diamyldithiocarbamate additive combination for use in soap based greases. The combination provides excellent to exceptional EP performance with reduced levels of environmentally undesirable antimony heavy metal. However, the composition has a tendency to corrode copper and steel at concentrations>2.00 mass percent.